Jesus wasn't born on December, but there was a festival then, called 'marx' in this period, people do worshiped god of "sun" but after Jesus was born, He was proclaimed as a savior and also king, to cut it short there was a king after the death of Jesus Christ who converted to Christian due to some reasons; He was the one who stopped his people of been worshiped and celebrating the god of sun "Marx" since then Jesus Christ was proclaimed to be celebrating instead of god of sun " Marx". This is where Christmax was derived. The name of the king is Constantine in 378AD

Let nobody fool you about Xmas...